Energy harvesting mechanism for medical devices

ABSTRACT

Embodiments of the invention provide apparatus, systems and methods for harvesting energy from bio-kinetic events to power various implanted medical devices. One embodiment provides an energy harvesting mechanism for a cardiac pacemaker comprising an energy converter and a signal path component. The energy converter is positionable inside a human body and configured to generate electric power signals in response to a bio-kinetic event of the human body such as a heart beat, respiration or arterial pulse. The converter can comprise a piezoelectric material which generates electricity in response to mechanical deformation of the converter. The converter can also have a power generation characteristic that is matched to the frequency of the bio-kinetic event. For heart beat powered applications, the power generation characteristic can be matched to the physiologic range of pulse rates.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/561,159 entitled “ENERGY HARVESTING MECHANISM FOR MEDICAL DEVICES”,filed Sep. 16, 2009, which application claims the benefit of ProvisionalU.S. Patent Application No. 61/099,203, filed Sep. 23, 2008, entitledENERGY HARVESTING MECHANISM FOR MEDICAL DEVICES. The aforementionedapplications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the invention relate to energy harvesting mechanisms.More specifically, embodiments of the invention relate to the use ofenergy harvesting mechanisms for powering implanted medical devices suchas pacemakers, defibrillators and other devices.

A number of implantable electronic medical devices such as cardiacpacemakers and implantable defibrillators utilize a battery powersource. The operational life of many of these devices is limited by thelife of the battery. While there have been many advances in portablebattery technology, most current devices do not last longer than tenyears at which time, the pace maker must be removed. Also, manybatteries undergo a certain amount of self-discharge so even if thepacemaker or other devices is not drawing current battery failure willstill occur over time. Battery failure can be sudden or occur through adrop off in battery voltage. Whatever the cause, battery failure can bea life threatening event requiring immediate intervention includingsurgery. Thus there is a need for improved power sources for cardiacpacemakers and other implanted medical devices

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention provide apparatus, systems and methods forharvesting energy from biokinetic events to power various implantedmedical devices. One embodiment provides an energy harvesting mechanismfor a cardiac pacemaker comprising an energy converter and a signal pathcomponent. The energy converter is positionable inside a human body andconfigured to generate electric power signals in response to abio-kinetic event of the human body such as a heart beat, respiration orarterial pulse. The converter can also have a peak generated voltage orother power generation characteristic (e.g., root mean square generatedvoltage or voltage), that is matched to the frequency of the bio-kineticevent. For heart beat powered applications, the power generationcharacteristic can be matched to the typical physiologic range of pulserates, e.g., 40 to 180 beats per minute. It can also be matched to thepulse range for a particular patient. As is explained below, theconverter can also be configured to generate electricity for deformationin any or all three axis's. Also, the energy converter can be figured togenerate electric power independent of a plane of deformation of theconverter.

Typically, the current generated by deformation of the converter is AC,but it can be rectified to generate DC. The converter can be sized orotherwise configured to generate sufficient electrical power to powerthe entire pacemaker (or other device) or to supplement the current froma pacemaker battery, allowing for longer battery life as well asproviding a backup should the battery fail. Power management circuitrycan be used to switch between use of battery power or the converter asthe power supply as well as charge the battery by a trickle charge orother charging regimen. In particular embodiments, the converter can beconfigured to generate between 20 to 40 μamps of current.

In many embodiments, the energy converter comprises a piezoelectricmaterial which generates electricity in response to mechanicaldeformation of the converter. The converter is desirably positioned todeform in response to motion from the heartbeat or other bio-kineticevent so that with each heartbeat, the converter generates electricalpower to power the pacemaker. The thickness and material properties ofthe converter can be configured to have a stiffness/flexibility whichallows for a peak generated voltage, current etc, for a frequency ofconverter deformation within the physiological range of pulse rates.They can also be configured so the converter has a resonant frequencywithin this range of these pulse rates.

In many embodiments, the piezo-electric material comprises a bundle ofpiezo-electric fibers which are arranged around a core conductor. Thepiezo electric fibers are of a sufficient number and arrangement suchthat when the bundle is deformed in a given direction at least one fiberwill be deformed sufficiently to generate sufficient energy for thepacemaker or other selected device. Thus, the bundle can generatevoltage from deformation in any direction as opposed to only one or alimited number of directions.

The signal path component is structured to enable the power signals tobe carried from the energy converter to the cardiac pacemaker. In manyembodiments, the signal path component comprises a cable or lead thatcarries pace making signals to the heart. Typically, the energyconverter will be positioned in the cable so that movement of the cablefrom the beating heart provides the kinetic energy for energyconversion. Other configurations are also contemplated, such asattaching the converter to the cable or to a container housing thepacemaker electronics.

The cable or lead can include at least a first wire for carrying thepacemaker signal to the heart and at least a second wire for carryingpower signals to the pacemaker. Typically, the energy converter isshaped to fit within cable. The converter can be coaxial with respect tothe cable and can have a form factor or shape that does not change theform factor of the cable. In this way, no additional volume is requiredfor integrating the converter into the cable.

In a preferred embodiment, the converter can have a rod or cylindricalshape in a non-deformed state. In such embodiments, bending or flexingof the rod provides the deformation that causes energy generation. Thestiffness of the rod can be configured to cause selectable amounts ofbending and produce a particular maximum voltage for a given frequencyof deformation from a heart beat or other bio-kinetic event. The rod orother shaped converter can also be configured to generate voltage frommultiple types of deformation such as bending twisting, pulling,compression and combinations therefore.

The rod can also be tapered, articulated, crimped or otherwiseconfigured to bend at particular location or locations on the rod so asto generate the maximum amount of voltage. In particular embodiments,the rod can have a stiffness profile configured to optimize thegeneration of electric current depending the position of the lead in theheart, position of the converter in the lead, heart rate or otherfactor. Stiffer profiles can be selected for locations likely to producegreater amounts of deformation and versa visa. All or a portion of therod can also be pre-shaped to have a curved or other shape with springmemory so that rod will bend from motion of the heart or otherbio-kinetic event and then spring back to its original shape. The shapeof the curve can match a shape of the ventricle in its contracted orexpanded state so that electrical energy can be generated duringsystole, diastole or both.

The portion of the cable or lead containing the energy converter isdesirably placed on, in or near the heart so that it is flexed orotherwise moved by the motion of the heart. The energy converter canalso be placed in a selected location in the lead so as generate aselectable amount of current from deformation of the lead. For example,the converter can placed in a portion of the cable lead is positioned onor near the apex of the heart. The lead can also include multiple energyconverter portions, positioned at selectable locations in the lead so asto have multiple locations for energy generation. The lead can also betapered or articulated so as to bend or otherwise deform at theparticular locations where the energy converter is positioned. In someembodiments, the energy converter can even be embedded into the heartwall (e.g., using a helical or other anchor) so as to be deformed duringmotion of the heart.

In another aspect of the invention, a rechargeable power supply can becoupled to a wire, cable or other signal path component and configuredto receive electrical energy generated by the energy converter. Invarious embodiments, the power supply can include a rechargeablebattery, capacitor or other electrical storage means. In these andrelated embodiments, the power supply can be configured to provide powerfor a selectable period should the patient's heart stop or develop anarrhythmia, other rhythm abnormality (e.g., fibrillation) or othercondition which prevents adequate power generation for pacing or otherfunction. The rechargeable power supply can also be used to perform asecondary function such as defibrillation. Power management circuitryand regimens can be employed to recharge the power supply while stillmaintaining sufficient current and voltage for pacing. In oneembodiment, a trickle charge regimen can be used. A duty cycle approachcan also be employed to divert power during portions of the cardiaccycle that do not require pacing. In other embodiments, EKG monitoringcircuitry can be used to determine when pacing is not required and thensend a signal to the power management circuitry to divert power to therechargeable power supply. A combination of these approaches can also beemployed.

In still another aspect of the invention, embodiments of the energyconverter can also be used as a sensor to sense various mechanical andelectrical properties of the heart including heart rate, rhythm (e.g.,normal sinus rhythm, arrhythmia, pvc, etc.), wall motion abnormalities,myopathy, ventricular hypertrophy and related condition. One or more ofthese conditions can be detected through means of an algorithm thatanalyzes one or more of voltage, current or power wave forms generatedby the energy converter. Specifically the algorithm can be configured todetect changes in amplitude, frequency of the wave form or both. Whenamplitude (voltage or current) or frequency falls below a threshold asignal can be sent to a controller, power management circuitry ortelemetry circuitry to alert the patient or a medical professional.Changes can also be detected using derivative or integral functions. Forexample, a derivative function can be used to look for rates of changein amplitude. An integral function can be used on one or more curves,for example to look for changes in total work done over time. Energyconverters can also be configured and positioned to sense otherbio-kinetic data such as respiration rate, blood pressure, heart valvefunction and other related functions.

Embodiments of the energy converter can be configured to simultaneouslyperform energy harvesting and sensing. Multiple converters can be placedin one or more pacemaker leads so as to sense in one or more locationsto create a map of heart wall motion, rhythm or other cardiac functionor property. Similar approaches can be used to map the motion of otherbio-kinetic events such as respiration, peristaltic waves or otherdigestive motion, arterial pulsation and like motions. Further detailsof these and other embodiments and aspects of the invention aredescribed more fully below with reference to that attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a lateral view showing an embodiment of an energy harvestingsystem for a pacemaker or other cardiac device.

FIG. 1 b is a lateral view showing the electrical connections and signaldirection for a cardiac device energy harvesting system.

FIG. 1 c is a graph illustrating a stiffness profile for a rod shapedembodiment of the energy converter

FIG. 1 d is a lateral view showing an embodiment of a curved energyconverter positioned in the ventricle.

FIG. 2 is a perspective view illustrating an embodiment of an energyconverter made up of a bundle of piezo-electric fibers.

FIG. 3 a is a lateral view showing an embodiment of an energy harvestingsystem for a cardiac pacemaker where energy is generated fromdeformation of a cardiac pacemaker lead containing an energyconverter/energy harvesting device.

FIG. 3 b is an expanded view of the embodiment of FIG. 3 a showing thepositioning of an energy harvesting pacemaker lead in the ventricle ofthe heart.

FIG. 3 c is an expanded view of the embodiment of FIG. 3 a showing thedeformation of the pacemaker lead and energy converter caused by thecontraction of the ventricle.

FIG. 3 d is a lateral view showing an embodiment of an energy harvestingdevice comprising a patch or layer positioned adjacent the ventricularwall or a vane positioned on the cardiac pacemaker lead away from theventricular wall.

FIG. 4 is a schematic view illustrating an embodiment of a circuitarchitecture for converting power signals from an energy harvestingdevice for use by a cardiac pacemaker.

FIG. 5 is a schematic view illustrating an embodiment of an energyharvesting circuit architecture for powering a cardiac pacemaker wherethe architecture includes a rechargeable battery.

FIG. 6 is a schematic view illustrating an embodiment of a circuitarchitecture for converting power signals from an energy harvestingdevice for use by a cardiac defibrillator.

FIG. 7 is a lateral view illustrating use of an energy harvesting deviceas a sensor for detecting conditions of the heart.

FIG. 8 shows an EKG and a corresponding electrical waveform generated byan energy harvesting device coupled to a pacemaker lead in the heart.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention provide apparatus, systems and methods forusing energy harvesting materials, such as piezo electric materials, topower various implanted electronic medical electronic devices such asimplantable cardiac pace maker devices. Referring now to FIGS. 1 a-1 b,one embodiment of an energy harvesting system 10 for powering animplanted cardiac pacemaker, or other electronic medical device 20includes a cable 30 having an energy converter 40 that sends electricalpower signals 50 via a signal path component 60 such as a wire. Invarious embodiments, device 20 can comprise an implantable cardiacdefibrillator, cardiac telemetry device, cardiac assist device, and/oran implantable pump (e.g., an insulin pump). For ease of discussion, thefollowing description of various embodiments of system 10 will bereferring to device 20 as an implanted cardiac pacemaker 20. Suchembodiments will also be referring to cable 30 as a cardiac lead 30.However, it should be understood that system 10 can be readily adaptedfor use with one or more other devices 20 and cables 30.

Lead 30 has a distal end 31 which includes an electrode 32 for providinga pacing signal 33 via one or more dedicated pacemaker wires 34 withinlead 30. The lead also has one or more wires which serve as signal pathcomponents 60 for sending a power signal 50 to the pacemaker or otherdevice 20. In specific embodiments, the lead can include a first andsecond wire 61 and 62 for sending a first and second power signal 51 and52, for example one higher voltage and one lower voltage so as to powerdifferent components of device 20 or another device (not shown). Wires60 can also be used for sending signals 50 to converter 40, for example,to activate one or more switches within the converter (not shown) todynamically reconfigure the power generation characteristics of theconverter. A portion of wires 60 can comprise the core conductor offiber bundle 42 described below.

Energy converter 40 converts mechanical energy into electrical energyand when placed in proximity to various moving body tissues orstructures and can be used to harvest energy from the movement of thosetissues/structures caused by a biokinetic event such as heart beat(thus, energy converter 40 is also described herein as an energyharvesting device 40). Typically, converter 40 comprises atransconductive material that converts mechanical energy into electricalenergy. In many embodiments, energy converter 40 comprises apiezoelectric material which generates electrical energy in response tomechanical deformation of the converter. The converter 40 is desirablypositioned in lead 30 to deform in response to motion from the heartbeatso that with each heartbeat, the converter deforms to generateelectrical power to power pacemaker 20. Thus in these and relatedembodiments, converter 40 has a deformed and a non-deformed state.

Converter 40 can be sized or otherwise configured to generate sufficientelectrical power to meet all of power needs of pacemaker 20 or tosupplement the current from a pacemaker battery or other power supply,allowing for longer battery life as well as providing a backup shouldthe pacemaker battery fail. Power management circuitry (described below)can be used to switch between use of battery power or the converterdepending upon the charge level of the battery and/or the powerrequirements of the pacemaker or other device 20. In variousembodiments, the converter can be configured to generate between 10 to100 μamps of current with specific range of 20 to 40 μamps; greater andlesser ranges are also contemplated.

The thickness and material properties of converter 40 can be configuredto have a stiffness/flexibility which allows for a peak generatedvoltage or other power generation characteristic that is matched to thenormal physiological range of pulse rates e.g. 40 to 180 (which alsocorresponds to the rate of deformation of the converter). Other powergeneration characteristics which can be so matched include, root meansquare generated voltage, peak generated current or root mean squaregenerated current. In this way, the power generation characteristics ofthe converter can be optimized for use in pacing and various othercardiac applications. In other non-cardiac embodiments, the powergeneration characteristics can be matched to the frequency of otherbio-kinetic events such as respiration rate.

For embodiments where converter 40 is placed on or in lead 30, theconverter 40 can have a variety of shapes and spatial arrangements withrespect to the lead. For example, the converter can have a cylindricalor rectangular shape that is coaxial with respect to longitudinal axis30 a of lead 30. Other shapes and arrangements are also contemplated.For example, the converter can comprise a tube or layer that ispositioned over or within lead 30. The converter can also have a formfactor or shape 40 s, that does not appreciably change the form factoror shape 30 s of lead 30. In this way, no additional volume is requiredfor integrating the converter into the lead. In a preferred embodiment,converter 40 can have a rod shape 40 r in its non-deformed state. Insuch embodiments, bending or flexing of the rod provides the deformationthat causes the generation of electrical energy. The stiffness of therod can be configured to cause selectable amounts of bending and producea particular maximum voltage for a given frequency of deformation from aheart beat or other bio-kinetic event. Rod 40 r or other shapedconverter 40 can also be configured to generate electrical energy frommultiple types of deformation such as bending twisting, pulling,compression and combinations therefore. Further, rod 40 r or otherenergy converter 40 can be configured to generate electric powerindependent from a plane of deformation of the energy converter.

Rod 40 r can also be tapered, articulated, crimped or otherwiseconfigured to bend at particular location or locations so as to generatethe maximum amount of voltage. As is shown in FIG. 1 c, variousembodiments of rod 40 r or other converter 40 can have a stiffnessprofile 40 sp configured to optimize the generation of voltage dependingupon the position of the lead in the heart, position of the converter inthe lead, heart rate or other factor. In the embodiment shown in FIG. 1c, the stiffness profile is configured to produce deformation near themid portion of the converter rod. Other profiles are also contemplated,such as a stiffness profile with a maximum stiffness in the center ofthe rod and decreasing profiles towards the ends so as to produce abending deformation along the entire length of the converter. In anotherembodiment, the converter can be configured to have a sinusoidal likestiffness profile along its length so as to produce a standing wave ofbending motion and deformation. Stiffer profiles can be used forlocations likely to produce greater amounts of deformation and viceversa. The stiffness profile can be selected to produce a resonantfrequency which is within the range of physiological heart rates for thepatient or a patient population to which the patient belongs.

In various embodiments, all or a portion of rod 40 r can be pre-shapedto have a curve or other shape 40 s with spring memory so that the rodwill bend from motion of the heart or other bio-kinetic event and thenspring back to its original shape. As is shown in FIG. 1 d, the shape ofthe curve 40 c can correspond to a shape Vs of the ventricular wall VWin its contracted or expanded state so that electrical energy can begenerated during systole, diastole or both. In particular embodiments,ultrasound or other medical imaging methods can be used to determine theshape and degree of curvature of the patient's ventricular wall and thenthis image can be used to custom fabricate the shape 40 s of converter40 using medical product fabrication techniques known in the art. Inuse, such embodiments allow for increased amounts of converterdeformation and thus voltage and power generation. Other shapes can beselected for positioning the converter in different locations in thebody

In many embodiments, converter 40 comprises a bundle 42 of piezoelectric fibers 43 which are arranged around a core conductor 44. Thepiezo electric fibers are of a sufficient number and arrangement suchthat when bundle 42 is deformed in a given direction, at least one fiber43 will be deformed sufficiently to generate sufficient energy for thepacemaker 20. In various embodiments, between 4 and 20 fibers can besymmetrically distributed around core 44, with specific embodiments of6, 8, 10, 12, 14 and 16. In a preferred embodiment, bundle 42 has sixfibers 43 symmetrically distributed around core 44. Also, preferably thediameter of fibers 43 is equal or less than that of core 44. In use,embodiments of bundle 42 allow for the generation of voltage and powerby the converter from deformation in any direction. Further descriptionof the use of piezoelectric fiber bundle as an energy converter is foundin U.S. Provisional Patent Application Ser. No. 61/095,619, entitledENERGY HARVESTING MECHANISM and U.S. patent application Ser. No.12/556,524, entitled ENERGY HARVESTING MECHANISM; the aforementionedapplications being fully incorporated herein by reference for allpurposes. Other materials can also used for fibers 43 including variouselectret and pettier materials known in the art.

Referring now to FIGS. 3 a-3 d, typically lead is 30 positioned inventricle V such that distal end 31 makes contact with the endocardialsurface ES of the ventricular wall VW. This allows electrode 32 to be inelectrical conduct with surface ES so as to conduct signal 33 to theventricle of the heart (lead 30 can also be positioned in the atria ofthe heart so as to make contact with the atrial wall). In many cases,the distal end of the lead can include a fixation device (not shown)such as a helical tip that allows the lead to be fixed to theventricular wall (as is shown in FIG. 3 b) or other portion of the heartwall. The portion 35 of lead 30 containing energy converter 40 isdesirably placed within a location in the ventricle V or other portionof the heart H so that it is flexed or otherwise deformed by the motionof the heart. For example, in the embodiment shown in FIG. 3 b, theconverter can placed in lead portion 35 that is positioned near the apexAx of the heart. This allows the converter to be bent and otherwisedeformed with each contraction of the ventricle as is shown in FIG. 3 c.Lead 30 can also include multiple energy converters 40 positioned atselectable locations in the lead so as to have multiple locations forelectrical energy generation. For example, the energy converter caninclude a first energy converter positioned in a first location and asecond energy converter positioned at a second location. The firstenergy converter can be configured to generate energy during a firstportion of the bio-kinetic event and the second energy converterconfigured to generate energy during a second portion of the bio-kineticevent. The bio-kinetic event can be a heartbeat, where the first portionof the event is systole and the second portion is diastole. Energyconverter 40 can even be embedded into the ventricular wall itself(e.g., using a helical or other anchor) so as to be directly deformed bythe motion of the heart. In such embodiments, the converter 40 isdesirably fabricated from a flexible material so as to not mechanicallyimpede the contractile motion of the heart. The converter 40 can beconfigured to have a stiffness profile that allows for maximum amountsof deformation of the converter during the course of a heart beat whileminimizing any forces impeding contraction of the chambers of the heartsuch as the left ventricle. This can be achieved by configuring thebending stiffness of the converter to be less than the forces developedby the contracting chambers of the heart. In particular embodiments, thebending stiffness can be less than contractile forces of particularchambers of the heart (e.g., the left ventricle) by a factor in therange of 1.5 to 20 times, with specific embodiment of 2, 4, 6, 8, 10,14, 16 and 18 times). Other ratios are also contemplated.

Referring now to FIG. 3 d, in other embodiments, converter 40 cancomprise a thin patch or layer 47 that is attached to the distal end 31of lead 30 and also rests against the ventricular wall VW. Layer 47 isdesirably made of a very thin flexible material and is deformed eachtime the ventricle contracts and relaxes. Layer 47 can have a variety ofshapes but is desirably circular or oval. In another embodiment,converter 40 can comprise a vane or blade 48 that is attached to lead30. Vane 48 has a shape and size configured to be deformed by flowingblood in the ventricle (or atria) while minimizing blood cell lysis. Invarious embodiments, vane 40 can comprise a circular or oval shape. Thevane can also be coated with one or more non-thrombogenic coatings knownin the art (e.g., silicone, etc) including various drug elutingcoatings.

Referring now to FIGS. 4-6, various circuit architectures can beemployed for utilizing energy from embodiments of harvesting energydevices described herein to power a cardiac device such as an implantedcardiac pacemaker or cardiac defibrillator. One embodiment of a circuitarchitecture 70 for using an energy harvesting device or converter 40 topower a cardiac pacemaker 20 is shown in FIG. 4. In this and relatedembodiments, architecture 70 can include converter 40, a rectifyingcircuit 80 for rectifying AC to DC voltage, a first capacitor 90, asecond high value capacitor 100, a DC to DC converter 110 and pacemakingdevice 20. In many embodiments, the voltage generated by deformation ofthe converter 40 is AC and can be rectified to generate DC using arectifying circuit 80. In preferred embodiments, circuit 80 can comprisea bridge circuit 81 using one or more Schottky diodes 82. Also, a DC toDC converter 110 can be used for stepping up or stepping down voltagefor the pacemaker. Converter 110 can be linear, switch mode or magnetic.Capacitor 100 can have sufficient capacitance to power the pacemaker forshort periods of time. In the embodiment shown, the pacemaker 20 has apower requirement of between 50-100 μw. Converter 40 can be configuredto meet all or a portion of this power requirement. All or a portion ofthe components of architecture 70 can be contained in an applicationspecific integrated circuit or ASIC.

In another embodiment shown in FIG. 5, architecture 70 can include arechargeable power supply 120 such as a rechargeable battery 121, orlike device along with charging circuitry 130. Suitable rechargeablebatteries include nickel cadium, lithium, lithium ion cell, lead acidand like chemistries. Power supply 120 can be configured to providepower for a selectable period should the patient's heart stop or developan arrhythmia, or other condition which prevents adequate powergeneration by converter 40 for pacing or other function. Chargingcircuit 130 can include or otherwise be coupled to power managementcircuitry 135 that employs one or more power management regimens oralgorithms 136 (via hardware or software). Power management circuitry135 (see FIG. 7) and regimens 136 can be employed to recharge powersupply 120 while still maintaining sufficient current and voltage forpacing. In one embodiment, a trickle charge regimen can be used. A dutycycle approach can also be employed to divert power during portions ofthe cardiac cycle that does not require pacing. In other embodiments,EKG monitoring circuitry can be used to determine when pacing is notrequired and then signal to the power management circuitry to divertpower to the rechargeable power supply. A combination of theseapproaches can also be employed.

In another embodiment of an energy harvesting circuit architecture 70shown in FIG. 6, architecture 70 can be configured to meet the powerneeds of an implantable cardiac defibrillator (ICD) device 220. In theseand related embodiments, architecture 70 can include a high voltagearchitecture 270 and a low voltage architecture 370. High voltagearchitecture 270 is used to power a high voltage circuit 221 ofdefibrillator 220 that is in turn used to charge a defibrillatorcapacitor 222. Architecture 270 can include charging circuitry 230 and arechargeable battery 220. Low voltage architecture 370 is used to powera low voltage circuit 371 of defibrillator 220 and can include a bridgecircuit 380, a dc to dc converter 390 and a large value capacitor 400and a capacitor 410.

Referring now to FIGS. 7-8, in various embodiments, energy converter 40can also be used as a sensor 340 to sense properties of the heart orother organ or tissue. Sensor 340 generates a voltage or otherelectrical waveform 350 that is produced by motion of the heart causingdeformation of the sensor. Waveform 350 is affected by variouscharacteristics of heart motion including heart rate and wall motion.These characteristic affect one or more of the frequency, amplitude andshape of the wave form. Accordingly, in addition to its use in poweringcardiac pacemaker or other cardiac device 20, waveform 350 can be usedto analyze and measure various properties of the heart. Such propertiescan include heart rate; rhythm (e.g., normal sinus rhythm (NSM)arrhythmia, pvc's, etc.) and wall motion abnormalities, myopathy,ventricular hypertrophy and related conditions. In the embodiment shownin FIG. 8, waveform 350, can be correlated to the patient's EKG 355 andused to analyze changes in the EKG to ascertain whether the heart is innormal sinus rhythm 356 or has gone into fibrillation 357. In the latercase, fibrillation or other motion abnormality can be detected by asudden decrease in the amplitude of voltage waveform 350 as may beindicated by an inflection point 350 i in curve 350.

In various embodiments, sensor 340 can comprise a plurality 341 ofsensors 340 that are placed at various locations along lead 30. Theplacement of sensors 340 can be in a pattern 342 so as to generate a map343 of heart wall motion. Map 343 can be used to analyze heart wallmotion including propagation of waves of contraction and relaxation inthe heart wall along whole sections of the ventricle or atria. Map 343can also be used to generate a wall motion score index for the mappedregion of the ventricle. In one embodiment, the plurality 341 of sensors340 can comprise at least three sensors that are positioned in lead 30as to be located in the top, middle and apex portions of the heart. Thisallows for the detection of the wave of ventricular wall contractions asit moves from the apex through the upper/superior portions of ventricle.Time and/or phase lags between the waveforms 350 generated at eachsensor 340 in the pattern can also be used to deduce various wall motionabnormalities such as regional akinesia.

Sensor 340 can be coupled to a monitoring device 360 which includes acontroller 372 and a display 380. Sensor 340 signals a waveform signal351 to device 360 and controller 372. Controller 372 can include one ormore algorithms 375 resident in memory resources 376 coupled to thecontroller for analyzing signal 351. Suitable memory resources includeRAM, ROM, DRAM and other electronic memory resources known in the art.Algorithms 375 can analyze one or more of the voltage, current or powerwave forms generated by sensor 340. Specific embodiments of algorithms375 can be configured to detect changes in amplitude, frequency of waveform 350 or both. Detection and analysis of these changes can be usedboth for patient diagnostic and power management purposes. For example,when the amplitude (e.g., voltage) or frequency of the waveform fallsbelow a threshold, a signal can be sent to a controller or telemetrycircuit coupled to or resident within device 20 to alert the patient ormedical professional. Signals can also be sent to power managementcircuitry 135 to switch to battery power from battery 120 or other powersupply. Changes in waveform 350 can also be detected using derivative orintegral functions. For example, a derivative function can be used tolook for rates of change in amplitude. An integral function can be usedon one or more curves, for example, to look for changes in total workdone over time. Other numerical methods and pattern recognitionalgorithms known in the art can also be employed (e.g., fourieranalysis. fuzzy logic algorithms, etc.)

In various embodiments, sensor 340 and/or device 20 can include an RFcommunication chip or like device for wirelessly signaling device 360using BLUE TOOTH or other RF communication protocol. Other means ofmedical telemetry known in the art are also contemplated. In these andrelated embodiments, monitoring device 360 can be worn by the patient orplaced within proximity of the patient. It may also be integrated intovarious portable communication devices such as cell phones, PDA's andlike devices that the patient wears or places in proximity to theirperson. In these and related embodiments, when a condition warrantingalerting of the patient is detected (e.g., an arrhythmia), a signal issent to device 360, device 360 can concurrently sound an alarm and alsosend a signal over a wireless phone or other network (e.g., theInternet) to alert the patients doctor, nurse or other medical careprovider.

CONCLUSION

The foregoing description of various embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to limit the invention to the precise forms disclosed. Manymodifications, variations and refinements will be apparent topractitioners skilled in the art. For example, various embodiments ofthe energy harvesting mechanisms can be sized and otherwise adapted forplacement in variety of locations in the body including withoutlimitation the abdominal cavity, the chest cavity and the extremitiesand adapted to utilized particular bio-kinetic events in those locationssuch as peristaltic waves, respiration/diaphragm movement or any numberof muscle contractions or movement of a limb. Various embodiments canalso be configured placed in the heart or arterial system to utilize anarterial pulse to produce deformation of the energy converter. Also,embodiments of the energy harvesting mechanism can be sized or otherwiseadapted for various pediatric and neonatal applications.

Elements, characteristics, or acts from one embodiment can be readilyrecombined or substituted with one or more elements, characteristics oracts from other embodiments to form numerous additional embodimentswithin the scope of the invention. Moreover, elements that are shown ordescribed as being combined with other elements, can, in variousembodiments, exist as standalone elements. Hence, the scope of thepresent invention is not limited to the specifics of the describedembodiments, but is instead limited solely by the appended claims.

What is claimed is:
 1. An energy harvesting mechanism for a cardiacpacemaker, the mechanism comprising: an energy converter positionableinside a human body to generate electric power signals in response to abio-kinetic event of the human body; the energy converter having acharacteristic matched to the frequency of the bio-kinetic event; and asignal path component structured to enable the power signals to becarried from the energy converter to the cardiac pacemaker.